Insert and read Image in QLable using QDataWidgetMapper

[hsm13]

I have simple master detail application using QDataWidgetMapper in master table; I added a blob in database and QLable to show the picture and button to select a picture

The button code

QString pix = QFileDialog::getOpenFileName(
                 this, tr("Open file"), "/MyDocument/", tr("PNG Images (*.jpg)") );
 
     QImage image(pix);
     ui->pix_label->setPixmap(QPixmap::fromImage(image));

QString pix = QFileDialog::getOpenFileName(
                 this, tr("Open file"), "/MyDocument/", tr("PNG Images (*.jpg)") );

     QImage image(pix);
     ui->pix_label->setPixmap(QPixmap::fromImage(image));

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and the classic mapper code

mapper = new QDataWidgetMapper(this);
    mapper->setModel(model);
    mapper->setItemDelegate(new QSqlRelationalDelegate(this));
    mapper->setSubmitPolicy(QDataWidgetMapper::ManualSubmit);
    mapper->addMapping(ui->id,model->fieldIndex("id"));
    mapper->addMapping(ui->fName,model->fieldIndex("fName"));
    mapper->addMapping(ui->lName,model->fieldIndex("lName"));

mapper = new QDataWidgetMapper(this);
    mapper->setModel(model);
    mapper->setItemDelegate(new QSqlRelationalDelegate(this));
    mapper->setSubmitPolicy(QDataWidgetMapper::ManualSubmit);
    mapper->addMapping(ui->id,model->fieldIndex("id"));
    mapper->addMapping(ui->fName,model->fieldIndex("fName"));
    mapper->addMapping(ui->lName,model->fieldIndex("lName"));

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Now, I tried to add this line but couldn't navigate pictures

mapper->addMapping(ui->picture_label,model->fieldIndex("picture"));

mapper->addMapping(ui->picture_label,model->fieldIndex("picture"));

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I need help to make that works, I'm a just beginner, so a detailed code is appreciated. Thanks in advance